1. Field of the Invention
This invention relates generally to improvements in flow control valves and, more particularly, but not by way of limitation, to a flow control valve having means within the valve body for forming simultaneously variable inlet and outlet orifices which are separated by an expansion chamber.
2. Description of the Prior Art
In the past, flow control valves have been generally constructed to have either a single variable orifice or at most a single set of simultaneously variable orifices. The species of flow control valves having a single orifice may be fairly represented by the apparatus shown in the following U.S. Pat. Nos.: 2,590,290; 2,912,011; 3,067,768; and 3,865,139. The species of flow control valves generally referred to as "multiple orifice valves" but which have only a single set of simultaneously variable orifices may be fairly represented by the apparatus shown in the following U.S. Pat. Nos.: 39,795; 1,192,689; 1,495,870; 1,738,135; 2,100,366; 3,026,899; 3,207,181; and 3,426,797.
While such valves are generally satisfactory in most flow control applications, it is common practice when severe cavitation is anticipated to utilize such valves in series since no single valve satisfactorily provides the necessary pressure drops. However, such series-connected valves are extremely awkward in operation and require extensive additional apparatus to accomplish precision flow control.